Architectural arrangement for bandwidth management in large central offices

Abstract

A new architectural arrangement for network elements deployed in a central office (CO) is disclosed. The architectural arrangement involves dividing the network elements into an optical layer comprised of elements that have optical signal interfaces and switch optical signals, an opto-electrical layer comprised of elements that have optical signal interfaces and switch electrical signals, and an electrical layer comprised of elements that have electrical signal interfaces and switch electrical signals. The opto-electrical layer connects the optical and the electrical layer, and also connects lower-rate optical links into the CO. This layered architectural arrangement allows for more efficient use to be made of the small number of high-rate ports supported in the optical layer, and for the off loading of switching responsibility from both the optical and the electrical layers. This, in turn, improves the overall performance and capacity of the CO. The opto-electrical layer can be implemented using known transport nodes that are only slightly modified for deployment within the CO environment.

We claim:  
     
       1. An arrangement of communications network elements at a central office (CO), comprising: 
       an optical layer of at least one network element, the element providing optical interfaces and optical space-switching, and the optical layer providing higher-rate optical switching between other elements in the CO;  
       an electrical layer of network elements, each element providing electrical interfaces and electrical space-switching, and the electrical layer connecting electrical links into the CO and providing electrical switching between elements in the CO; and  
       an opto-electrical layer of network elements, each element providing optical interfaces and electrical space-switching, and the opto-electrical layer connecting optical links into the CO, and being able to aggregate signals going to the optical layer into a lower number of higher-rate optical signals and to disaggregate signals coming from the optical layer into a higher number of lower-rate signals, connected to each other such that all signals flowing between the optical and electrical layers flow through the opto-electrical layer,  
       wherein the network elements in the opto-electrical layer are divided into at least one group, and the network elements comprising each group are all connected to a common node within that group such that the common node is the only node that is directly connected to the optical layer, and signals flowing from one node in that group to another node in that same group can be switched within the common node without going through either the optical or electrical layers.  
     
     
       2. The arrangement of claim  1 , wherein the network elements of the opto-electrical layer are Synchronous Optical Network (SONET) transport nodes. 
     
     
       3. The arrangement of claim  2  wherein at least one of the SONET transport nodes is an OC-192 node that is modified by programming it to additionally implement the time-slot interchange service and the intermediate path monitoring service. 
     
     
       4. The arrangement of claim  3  wherein the opto-electrical layer additionally provides electrical space-switching between its own elements using the modified node. 
     
     
       5. The arrangement of claim  1  wherein the common node is an OC-192 transport node. 
     
     
       6. The arrangement of claim  1  wherein a signal flowing from a transport node within a first group to a destination transport node within another group is aggregated with other signals into a higher-rate signal at the common node of the first group, sent as part of the higher-rate signal to the optical layer and then to the common node of the other group, disaggregated from the other signals comprising the higher-rate signal, and then sent from the other group's common node to the destination transport node for transmission from the CO. 
     
     
       7. The arrangement of claim  1  wherein the opto-electrical layer includes at least one transport node that does not connect optical links into the CO. 
     
     
       8. The arrangement of claim  1  wherein the electrical layer includes at least one digital signal cross-connect (DCS) switch. 
     
     
       9. The arrangement of claim  1  wherein the optical layer is implemented by one optical signal cross-connect (OXC) switch. 
     
     
       10. The arrangement of claim  1  wherein the network elements within the optical layer additionally connect optical protection-switching links into the CO, such that several COs are connected in a mesh in order to implement an alternate path of restoration service. 
     
     
       11. The arrangement of claim  10  wherein a full mesh is used. 
     
     
       12. The arrangement of claim  10  wherein a partial mesh is used. 
     
     
       13. The arrangement of claim  1  wherein the higher-rate optical switching provided by the optical layer operates at rates greater than or equal to the OC-48 rate. 
     
     
       14. An arrangement of communications network elements for interconnecting a large number of input and output links that converge at a central office (CO) comprising at least one set of transport nodes that connects optical links into the CO, said set being connected to both a digital signal cross-connect (DCS) switch that links electrical links into the CO, and an optical signal cross-connect (OXC) switch that provides high-rate connections between any sets of transport nodes in the CO, and wherein each set is comprised of a plurality of Synchronous Optical Network (SONET) transport nodes interconnected such that there is within each set a common node that is connected to all the other nodes within the set and to the OXC switch, and such that none of the other nodes within the set are connected to the OXC switch. 
     
     
       15. The arrangement of claim  14  wherein the common node is an OC-192 node and the other nodes in the set are lower rate SONET nodes.